Earlier studies of bovine erythropoietic ("congenital") porphyria will be expanded to include newly discovered animals with hereditary bovine protoporphyria. In addition to further characterization of the two diseases by chemical, histochemical and electron microscopy techniques, major emphasis will be given to 1) development of tests for the diagnosis of the carrier state, 2) therapeutic studies, and 3) isotopic studies of porphyrin biosynthesis in normoblasts of varying maturity, in reticulocytes, and in circulating red cells of different ages. BIBLIOGRAPHIC REFERENCES: Schwartz, S., L.W. Johnson, N. O'Connor, B.D. Stephenson, A.S. Anderson, and J. Johnson. Turnover of erythrocyte protoporphyrin, with special reference to bovine porphyria and to iron deficiency. Ann. Clin. Res., 8(Suppl. l7):203-212, 1976. Schwartz, S., B. Stephenson, D. Sarkar, H. Freyholtz, and W. Runge. Development and implications of experimental renal porphyria: Heme synthetase, ALA dehydratase, and porphyrins in liver, kidney, and Harderian glands of hamsters given DDC, estrogen, and/or cobalt. In Porphyrins in Human Diseases. M. Doss, Ed. S. Karger, New York, 1976. pp. 370-379.